Headlights dim or turn off/on at lower RPM's?

[Climb14er]

This has been happening more frequently the last six months.

Used to be once in a while, if I had a load on the electrical system, A/C, lights, turn signals, radio... when I was making a turn and RPM's dropped, the lights would dim momentarily and come right back up.

Lately, the lights are dimming longer and then coming back up, even with no load other than the lights.

I installed new battery back in the early part of the year.

Two months left on the extended warranty and Toyota called this... 'normal' two months ago. I say... b.s.!

Took my best friend out for dinner the other night, retired Naval Commander, 83 years young. Lights went out for two seconds as I was making a turn. He said to me... 'that's serious'! I said damn right.

Called the service manager yesterday and they're going to do a load test and overall test the alternator and charging system. They're going to charge me of course, nominal they said. If there's a problem, won't get charged and warranty will step in.

Anyone think of anything else other than an alternator that could be causing the lights to dim and come back up?

This is a first for me in any vehicle in many years.

 

[NorthShore4Runner]

Most likely just the alternator

 

[RunnerAK]

Yeah, sounds like your alternator is on its last legs, and despite what your dealer says, it is definitely not "normal" for a modern vehicle. I had an alternator fail on my previous vehicle and it had similar symptoms.

 

[Mike07SE]

Alternator for sure.

And at this point the replacement battery is just dying under all of the stress as well. Don't be surprised if they tell you the alternator needs replacement along with the battery.

 

[Climb14er]

Here's an update...

Took the 4Runner in to the Toyota dealer, lead mechanic, complete charging system check, load test, battery test...

Numbers were all fine! Totally freakin stumped by the continuing dimming of headlights!

Just the other night, was backing out of driveway at dusk, on the brake lightly, turned on the headlights and they went fully down... then came back up a second or two later.

Driving down the street five miles later, was in right land, put on left turn signal, lights went dim then up and then dim then came back up. Two seconds.

There seems to be a gremlin with the headlights dimming... slowing down- low rpm's, turn signals on at times, in park and moving to drive depressing brake... lights dim... at times... sporadically... and I can't figure it out. I'm stumped.

If it's not the alternator, what the heck could it be? :noidea:

 

[jonesmw10]

Ditto with what everyone is saying above, definitely the alternator. I just replaced my gf's alternator on her Taurus for the same reason. All tests showed it was good, but it wasn't.

 

[Climb14er]

We're going to escalate this problem. Major safety issue when lights dim and at times go totally out.

Thinking if there's a relay to the headlights that is weak or not getting enough juice.

Anyway, I searched this and couldn't find another instance with similar symptoms.

Could be alternator. Toyota possibly due to expense might be hesitant to send to extended warranty company without more verification.

Alternators on a V8 Toyota... not inexpensive.

 

[jonesmw10]

We're going to escalate this problem. Major safety issue when lights dim and at times go totally out.

Thinking if there's a relay to the headlights that is weak or not getting enough juice.

Anyway, I searched this and couldn't find another instance with similar symptoms.

Could be alternator. Toyota possibly due to expense might be hesitant to send to extended warranty company without more verification.

Alternators on a V8 Toyota... not inexpensive.

It could also be a bad ground or a loose connection on the battery/alternator. Were you able to check them out? You can look around the engine compartment and see the grounds (for the most part, I believe). I'd still say the alternator is on it's way out though, IMO

 

[Climb14er]

It could also be a bad ground or a loose connection on the battery/alternator. Were you able to check them out? You can look around the engine compartment and see the grounds (for the most part, I believe). I'd still say the alternator is on it's way out though, IMO

Yes... checked all grounds. Service Mgr asked me if any of the dash lights or warning lights came on when headlights dimmed or went out.

I told him only the headlights.

Could very well be the alternator, this was thought #1 from git go.

I'll let Toyota think this one through .. the shop foreman, lead mechanic and service mgr.

 

[470SNC]

definintely an alternator problem, happened to me on my FJ

 

[BlackWorksInc]

It does make me think of an alternator issue, the RPM dependency and the symptoms make me think the alternator can no longer provide adequate power at low RPMS.

Question, when you rev up the engine; do the lights start working again?

 

[gm350reratliff]

It could also be a bad ground or a loose connection on the battery/alternator. Were you able to check them out? You can look around the engine compartment and see the grounds (for the most part, I believe). I'd still say the alternator is on it's way out though, IMO

I would monitor the battery voltage while driving and having these symptoms.

I'm also thinking there could be a bad/weak body ground causing some of these issues. I would also check all the connections at the fuse box.